This proposed research will continue studies of the somatostatin-like peptides in rabbit retina. Somatostatin has been shown to be present i the rabbit retina in at least 4 forms: somatostatin-14, somatostatin-28, and 2-3 higher molecular weight forms. the main focus of the research will be the study of the release, biosynthesis and pharmacologic interactions of somatostatin-like peptides inthe retina maintained and perifused in vitro. The regulation of release of somatostatin-like immunoreactive materials by ions, by light and by pharmacologic agents including dopamine agonstists and antagonists and excitotoxic amino acids will be studied. An attempt will be made to correlate the rate of biosynthesis of the somatostatin-like peptides with the pharmacologic studies performed in vitro. These observations will be correlated with immunocytochemical studies of specific somatostatin binding sites. In particular, we shall determine the cell type and where possible, the neurotransmitter contents of cells making and reciving synapses with SLI-containing cells. It is hoped that these studies will begin to shed light on the role of somatostatin in the CNS in general, and in particular, its function in retinal physiology.